[PATCH 1/2] ARM: vexpress: refine MCPM smp operations override criteria
Sudeep Holla
sudeep.holla at arm.com
Mon Oct 17 10:31:58 PDT 2016
On 23/09/16 15:03, Lorenzo Pieralisi wrote:
> On Fri, Sep 23, 2016 at 02:09:06PM +0100, Lorenzo Pieralisi wrote:
>> Current vexpress smp init code detects whether to override the
>> default smp ops with MCPM smp ops by matching the "cci-400"
>> compatible string, in that MCPM requires control over CCI ports
>> to manage low-power states entry/exit.
>>
>> The "cci-400" compatible string check is a necessary but not
>> sufficient condition for MCPM to work, because the cci-400
>> can be made visible to the kernel, but firmware can nonetheless
>> disable non-secure CCI ports control, while still allowing PMU
>> access; if booted in non-secure world, the kernel would still
>> blindly override smp operations with MCPM operations, resulting
>> in kernel faults when the CCI ports programming interface is
>> accessed from non-secure world.
>>
>> This means that the "cci-400" compatible string check would
>> result in a false positive in systems that eg boot in HYP mode,
>> where CCI ports non-secure access is explicitly not allowed,
>> and it is reported in the respective device tree nodes with
>> CCI ports marked as disabled.
>>
>> Refactor the smp operations initialization to make sure that
>> the kernel is actually allowed to take control over CCI ports
>> (by enabling MCPM smp operations) before overriding default
>> vexpress smp operations.
>>
>> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
>> Cc: Liviu Dudau <liviu.dudau at arm.com>
>> Cc: Sudeep Holla <sudeep.holla at arm.com>
>> Cc: Nicolas Pitre <nicolas.pitre at linaro.org>
>> Cc: Marc Zyngier <marc.zyngier at arm.com>
>> ---
>> arch/arm/mach-vexpress/platsmp.c | 31 ++++++++++++++++++++++++-------
>> 1 file changed, 24 insertions(+), 7 deletions(-)
>>
>> diff --git a/arch/arm/mach-vexpress/platsmp.c b/arch/arm/mach-vexpress/platsmp.c
>> index 8b8d072..6cfd782 100644
>> --- a/arch/arm/mach-vexpress/platsmp.c
>> +++ b/arch/arm/mach-vexpress/platsmp.c
>> @@ -26,17 +26,34 @@
>> bool __init vexpress_smp_init_ops(void)
>> {
>> #ifdef CONFIG_MCPM
>> + int cpu;
>> + struct device_node *cpu_node, *cci_node;
>> +
>> /*
>> - * The best way to detect a multi-cluster configuration at the moment
>> - * is to look for the presence of a CCI in the system.
>> + * The best way to detect a multi-cluster configuration
>> + * is to detect if the kernel can take over CCI ports
>> + * control. Loop over possible CPUs and check if CCI
>> + * port control is available.
>> * Override the default vexpress_smp_ops if so.
>> */
>> - struct device_node *node;
>> - node = of_find_compatible_node(NULL, NULL, "arm,cci-400");
>> - if (node && of_device_is_available(node)) {
>> - mcpm_smp_set_ops();
>> - return true;
>> + for_each_possible_cpu(cpu) {
>> + bool available;
>> +
>> + cpu_node = of_get_cpu_node(cpu, NULL);
>> + if (WARN(!cpu_node, "Missing cpu device node!"))
>> + return false;
>> +
>> + cci_node = of_parse_phandle(cpu_node, "cci-control-port", 0);
>> + available = cci_node && of_device_is_available(cci_node);
>> + of_node_put(cci_node);
>> + of_node_put(cpu_node);
>> +
>> + if (!available)
>> + return false;
>> }
>> +
>> + mcpm_smp_set_ops();
>> + return true;
>> #endif
>> return false;
>
> For the records, while moving the code around I missed I was ending
> up with this idiotic double return, I have already reworked the patch
> and will squash changes in the final version if we agree on the bulk of
> the code.
>
I applied both patches to [1] with the fix for the above issue. Let me
know if that's fine. I have tested both hyp mode boot and SVC mode +
MCPM boot with latest u-boot by just fliping a bit in the firmware
(board.txt) without recompiling the kernel.
--
Regards,
Sudeep
[1] git.kernel.org/sudeep.holla/linux/h/vexpress/for-next
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